> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mobster.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Unable to launch app.mobster.wda.runner.xctrunner because the device was not, or could not be, unlocked.

> Your iPhone was locked when Xcode tried to start Mobster's helper. Unlock it and keep it unlocked. Mobster tries again by itself.

You see this: `xcodebuild` prints this (`com.apple.dt.deviceprep` code -3) when the phone is locked while Mobster starts its helper. Mobster shows `Unlock your iPhone. Mobster's helper starts as soon as it is unlocked.`

## Why it happens

iOS won't start UI automation on a locked phone. Mobster never enters your passcode and never unlocks the phone.

## Fix

1. Unlock the iPhone and keep it unlocked.
2. Wait. Mobster builds again by itself once the phone reads unlocked, and the helper starts about 2 seconds later.
3. For a phone that locks during unattended tasks, lengthen **Settings › Display & Brightness › Auto-Lock**.

## Check it worked

`mobster doctor` prints `✓ WebDriverAgent`. See also [the helper waits for unlock](https://docs.mobster.dev/troubleshooting.md#helper-waits-for-unlock).

Checked 26 Oct 2026 against Mobster 0.4.0. Back to [Troubleshooting](https://docs.mobster.dev/troubleshooting.md#iphone).


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